A new species of ice cream cone worm in the Gulf of California (Annelida, Pectinariidae)

BACKGROUND: Pectinaria Lamarck, 1818 is composed of 30 species, three of them were originally described from the west coast of the USA and Mexico: P.californiensis Hartman, 1941 (from Redondo Beach, California, USA), P.newportensis Hartman, 1941 (from Newport Bay, California, USA) and P.hartmanae Reish, 1968 (from Bahia de los Angeles, north-western Gulf of California, Mexico). NEW INFORMATION: A new pectinariid polychaete, Pectinariasantii sp. n., is reported from the central-eastern Gulf of California, Mexico. Pectinariasantii sp. n. is clearly distinguished from its congeners by a combination of the following morphological features: segment 4 with a ventral crest with six horn-shaped anterior projections; three chaetigers with notopodia (S5, S6 and S7); 12 chaetigers with noto- and neuropodia (from S8–19); 8–10 golden opercular paleae per lobe; a pair of ear-shaped lobes at the base of the cephalic veil; an anterior row of chaetae on notopodia with a deep incision and a bifid process at the lateral end of the shaft; and 13–21 pairs of amber scaphal hooks with distal margin rounded and hooded. A full description, including variation and photographs in live and fixed specimens, is provided, as well as a key to the species of Pectinaria from the Tropical Eastern Pacific and Temperate Northern Pacific.